1. Field of the Invention
The present invention relates to the field of underwater lighting.
2. Prior Art
The brightness of present LED based underwater lights is limited by the buildup of heat within the light fixture. This heat is generated by the LEDs themselves which, though more efficient than tungsten and many other light sources, still suffer from a less than 100% efficient conversion of input energy to light, the balance turning into heat, primarily at the light emitting diode junction, plus heat from the power supply and related control electronics that operate the LEDs.
Currently, the brightest underwater LED light fixtures are typically about 8 to 20 watts, with a few approaching 60 watts. Attempts to make these fixtures brighter by increasing either the power of the individual LEDs, or the quantity of LEDs, or both, have met with failure because of the increased internal heat within the waterproof housing, which dramatically shortens the operating life span of the LEDs, or causes significant color or output degradation, or destroys them entirely. Even the few fixtures that approach 60 watts do so only by becoming very large in size, to the point of being cumbersome and limited in applicability.
On the other hand, in non-submersible uses such as in theatre stage lights and outdoor concert lights, higher power LED fixtures are available, of the order of several hundred watts or more. This is because these fixtures' housings readily dissipate their internal heat away from the LED junctions by incorporating cooling openings and fans to vigorously draw atmospheric air into, through, and away from the LEDs or their heat sinks. Various additional fins and heat sink housings can also be attached to further the transfer of heat to the atmosphere. The cooling is facilitated by a nearly endless supply of relatively cool air in such applications.
However, none of the foregoing is effective when the entire light assembly has to be sealed inside a container that is submerged under water. In such a case, there is a very small amount of internal air, which rapidly becomes very, very elevated in temperature. The only means available for cooling is for the heat to be transferred from the LEDs to the air via convection or conduction, and from the air to the inner wall of the enclosure, then through the enclosure, and into the water. Some heat may travel by radiation from the LEDs (or power supply, etc.) directly to the inner wall of the enclosure, and then through the wall and out to the water. Still, heat buildup is the largest impediment to obtaining higher power underwater LED lighting. The largest impediment here is getting the heat from the air to the inner wall of the enclosure. The transfer from air to inner wall is very poor, and consequently, the air rises in temperature to the point where insufficient heat can transfer from the LEDs to the air until the LEDs reach a damaging, high temperature.